Pyridylalkyl phenyl ureas and their n-oxides

ABSTRACT

A method of improving the endogenous production of prostaglandins by a mammal is disclosed, which comprises administering to the mammal an effective amount of certain 1-pyridylalkyl-3-phenylureas. Disclosed also are novel substituted 1-pyridylalkyl-3-phenylureas and therapeutic compositions thereof which are useful in carrying out the method of the invention. 
     Disclosed also are methods of treating mammals for clinical conditions responsive to prostaglandins, such as, for example, male infertility, epidermal injuries, atonic uterine bleeding, thromboembolic disease and like clinical conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of our co-pendingapplication Ser. No. 428,361, filed Dec. 26, 1973 and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is concerned with the production of endogenousprostaglandins by mammals and more specifically concerns a method ofraising prostaglandin production levels in the mammal by administering1-pyridylalkyl-3-phenylureas. The invention also concerns a novel groupof substituted 1-pyridylalkyl-3-phenylureas and therapeutic compositionsthereof.

2. Description of the Prior Art

Natural prostaglandins are a well-known group of physiologically activeunsaturated hydroxy-substituted fatty acids which are biosynthesizedendogenously by mammals such as, for example, canines, bovines, equines,swine, and humans. Identified roles of the natural prostaglandins inmammalian physiology are illustrated by their action as mediators in theinflammatory process, as tonal agents in effecting the contractility ofsmooth muscle and as activators in a wide variety of mammalianreproductive processes.

Structurally, the natural prostaglandins have been arbitrarilyclassified into four basic families termed "PGE", "PGF", "PGA", and"PGB", respectively. The various families are composed of differinganalogs and stereoisomers having as a hypothetical parent structure,prostanoic acid. For example, the principal members of the PGE familyare 11α ,15-hydroxy-9-keto-prosta-13-enoic acid (referred toalternatively for convenience as "PGE₁ ");11α,15-dihydroxy-9-keto-prosta-5,13-dienoic acid (hereinafter referredto alternatively as "PGE₂ "); and11α,15-dihydroxy-9-keto-prosta-5,13,17-trienoic acid (referred toalternatively for convenience as "PGE₃ "). The principal members of thePGF family are 9α ,11α,15-trihydroxy-prosta 13 enoic acid (referred toalternatively for convenience as "PGF₁ α");9β,11α,15-trihydroxy-prosta-13-enoic acid (referred to alternatively forconvenience as "PGF₁ β"); 9α,11α,15-trihydroxy-prosta-5,13-dienoic acid(hereinafter referred to alternatively for convenience as "PGF₂ α");9β,11α,15-trihydroxy-prosta-5,13-dienoic acid (referred to alternativelyas "PGF₂ β"); and 9α,11α,15-trihydroxy prosta-5,13,17-trienoic acid(referred to alternatively as "PGF₃ α").

Physiological activity of specific natural prostaglandin compounds maybe the same, different in degree or differ from the physiologic activityof other specific natural prostaglandins. It appears, however, that theyall share a common property in not being continually produced andreleased by the mammalian tissues of origin. Instead, the prostaglandinsappear to be spontaneously synthesized in situ (biosynthesis beingequivalent to release) in response to certain stimuli or "trigger"mechanisms. The prostaglandins generally exhibit an extremely shortbiological half-life and current knowledge indicates that there is nostorage of prostaglandins by body tissues or fluids, with the possibleexception of seminal fluids. It has been suggested that the trigger orstimulus for endogenous prostaglandin synthesis is associated withtrauma of cellular membranes. Such trauma may occur through physical orchemical activity. For example, in the normal mammal carrying a fetus,circulating blood and amniotic fluids do not contain significant amountsof the prostaglandins PGE₂ and PGF₂ α until birth is imminent. At thattime the levels of PGE₂ and PGF₂ α produced by placental and uterinetissues rise substantially. The suggested function of the prostaglandinsat this stage of pregnancy is to stimulate uterine contractions, i.e.,labor induction. As another example, injury to mammalian epidermaltissue triggers the in situ synthesis of PGE₂ at the site of injury.PGE₂ is known to promote and accelerate healing of epidermal wounds(see, for example, U.S. Pat. No. 3,711,515 at Column 5, lines 1-11).

We have discovered that the quantity of prostaglandins producedendogenously by a mammal following the stimulation of biosynthesis willbe greatly enhanced, e.g., by from 5 to 10 percent to several timesnormal production, when certain 1-pyridylalkyl-3-phenylureas have beensystemically administered to the mammal prior to the stimulation ofbiosynthesis by normal trigger mechanisms.

Prior to our invention there was a suggestion that thrombin caused anincrease in the production levels of PGE₂ and PGF₂ α by mammalian bloodplatelets (Smith et al., Nature New Biol. 231-235).

Prior to our invention the treatment of clinical conditions responsiveto the presence of prostaglandins had been limited to the administrationof prostaglandins from exogenous sources. The method of our inventionhas a number of advantages over the administration of exogenousprostaglandins. For example, as mentioned above, the biologicalhalf-life of the naturally occurring prostaglandins is extremely short.Illustratively, it has been reported that after about 20 minutes, 500μg. of PGF₂ α administered intravenously to an adult human cannot bedetected in the body. Therefore, to treat clinical conditions such as anepidermal injury with exogenous sources of prostaglandins, it isnecessary to employ a continuous administration of the desiredprostaglandin over a prolonged period of time. By our method,therapeutic levels of the desired prostaglandin are delivered at the"target site" or site of injury with maximum efficiency. Sustained highlevels of prostaglandin are observed for several hours followingtreatment according to our method thus eliminating the need forcontinuous exogenous prostaglandin administration over long periods oftime. In addition, the systemic administration of exogenousprostaglandins delivers the prostaglandin to organs and tissues otherthan those at the desired target site. This may result in undesirableresponses or "side effects". By the method of our invention, therapeuticlevels of natural prostaglandins are produced at the target site, i.e.,at the point of epidermal injury or at the locality stimulatingsynthesis. This reduces the likelihood of responses in remotely locatedtissues, minimizing side-effects.

Prior hereto, a number of 1-pyridylalkyl and1-alkylpyridylalkyl-3-phenylureas were known. See, for example, U.S.Pat. Nos. 3,128,280; 3,700,678; Skinner, et al., J. Org. Chem. 25, 2046,(1960); Scully et al., J. Am. Chem. Soc., 75, 3400, (1973); Robison etal., J. Am. Chem. Soc., 77, 6554, (1955); Shibanov et al., U.S.S.R.,194, 825, (1967); Novikov et al., 2h. Prikl. Khim., 42, 2373 (1969; Jubyet al., J. Med. Chem., 10, 491, (1967); and Novikov, Khim. Geterotsikl.Soedin., (1), 115-116, (1968).

SUMMARY OF THE INVENTION

The invention comprises a method of increasing the production ofendogenous prostaglandins by a mammal which comprises administering tosaid mammal an effective amount of a compound selected from those offormula: ##STR1## pyridyl N-oxides thereof and pharmaceuticallyacceptable acid addition salts thereof wherein R₁ and R₂ are eachselected from hydrogen, halogen, hydrocarbyl having 1-6 carbon atoms,inclusive, alkoxy, alkylthio, nitro, amino, alkylamino, dialkylamino,acylamino and trihalomethyl; R₃ and R₄ are each selected from hydrogen,lower alkyl, alkenyl, cycloalkyl, aryl, aralkyl and aryl substitutedwith a group selected from halogen, lower alkoxy, and nitro; R₅ isselected from hydrogen, halogen, hydrocarbyl, alkoxy andhalogen-substituted hydrocarbyl with one to three halogen atoms; R₆ andR₇ are each selected from nitro, cyano, amino, acylamino, alkylamino,dialkylamino, alkylthio, arylthio, aryloxy and a group R₅ as previouslydefined; and n is an integer of from 1 to 2, inclusive; provided thatwhen one of R₅, R₆ and R₇ is chlorine, the pyridine ring moiety of thecompound (I) is attached to the rest of the molecule through the pyridylring carbon atom at the 4-carbon position.

Preferred for carrying out the method of the invention are thosecompounds (I) having the more specific formula: ##STR2## together withthe pyridyl N-oxides thereof and the pharmaceutically acceptable acidaddition salts thereof wherein n is as previously defined; R₈ and R₉ areeach selected from hydrogen, lower alkyl and phenyl; R₁₀ and R₁₁ areeach selected from hydrogen, halogen, lower alkyl, lower alkoxy,trihalomethyl and nitro provided that when one of R₁₀ and R₁₁ ischlorine, the pyridine moiety of the compound of Formula (II) isattached to the rest of the molecule through the pyridyl ring carbonatom at the 4-carbon position. Of the compounds (II), those having themore specific formula: ##STR3## pyridyl N-oxides thereof and thepharmaceutically acceptable acid addition salts thereof wherein R₁₂ andR₁₃ each represent hydrogen or lower alkyl; R₁₄ and R₁₅ are eachselected from hydrogen, halogen, lower alkyl, lower alkoxy andtrifluoromethyl are particularly preferred for carrying out the methodof the invention.

The invention also comprises novel compounds within the scope of Formula(I) and having the Formula (I) provided that when R₁ and R₂ are bothselected from hydrogen and alkyl, said novel compound is selected fromthose wherein R₇ is selected from cycloalkyl, aryl, aralkyl, alkenyl,cyano, amino, acylamino, alkylamino, dialkylamino, alkylthio, arylthioand those wherein R₄ is selected from cycloalkyl, aralkyl, aryl, andaryl substituted with a group selected from halogen, lower alkoxy, loweralkyl, nitro; and the pharmaceutically acceptable acid addition saltsthereof.

Preferred among the novel compounds of the invention for use in themethod of the invention are those of the more specific formula: ##STR4##the pyridyl N-oxides thereof and the pharmaceutically acceptable acidaddition salts thereof wherein n is as previously defined; R₁₆ and R₁₇are each selected from hydrogen and hydrocarbyl having 1 to 6 carbonatoms, inclusive; R₁₈ and R₁₉ are each selected from hydrogen, loweralkyl, lower cycloalkyl, and phenyl; R₂₀ is selected from cyano, alkoxyand alkylthio, and R₂₁ is selected from hydrogen, hydrocarbyl of one tosix carbon atoms, halogen, nitro, alkoxy, alkylthio andhalogen-substituted lower alkyl; provided that when R₂₁ is chlorine, thepyridine ring moiety of the compound (III) is attached to the rest ofthe molecule through the pyridyl ring carbon atom at the 4-carbonposition.

The term "halogen" is used herein in its conventional sense as embraciveof chlorine, bromine, fluorine and iodine and the term "halo" meanschloro, bromo, fluoro and iodo respectively.

The term "hydrocarbyl" is used throughout the specification and claimsas meaning the monovalent moiety obtained by removal of a hydrogen atomfrom a parent hydrocarbon, which contains 1 to 12 carbon atoms.Illustrative of such moieties are alkyl of 1 to 12 carbon atoms,inclusive, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,octyl, nonyl, decyl, undecyl, dodecyl and isomeric forms thereof;cycloalkyl of 3 to 8 carbon atoms, inclusive, such as cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and thelike; alkenyl of 2 to 12 carbon atoms, inclusive; such as vinyl, allyl,butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl,undecenyl, dodecenyl and isomeric forms thereof; aryl of 6 to 12 carbonatoms, inclusive, such as phenyl, tolyl, xylyl, naphthyl, biphenylyl andthe like, aralkyl of 7 to 12 carbon atoms, inclusive, such as benzyl,phenethyl, phenpropyl, phenbutyl, phenpentyl, phenhexyl and the like.When used in this specification and claims, the term "alkyl""cycloalkyl", "alkenyl", "aryl" and "aralkyl" have the meanings employedhere.

The term "halogen-substituted hydrocarbyl" means hydrocarbyl as definedabove wherein one or more hydrogen atoms have been replaced with ahalogen atom as defined above. Illustrative of halogen-substitutedhydrocarbyl are trichloromethyl, bromocyclobutyl, 1,2-diiodovinyl,chlorophenyl, p-chlorobenzyl and the like.

The term "alkoxy" is used herein to mean the monovalent moiety of theformula:-

    -- 0 -- alkyl

wherein alkyl is as described above. Illustrative of alkoxy are methoxy,ethoxy, butoxy, pentyloxy, heptyloxy, decyloxy, dodecyloxy and the like.

The term "alkylthio" means the monovalent moiety of formula:-

    alkyl -- S --

wherein alkyl is as defined above. Representative of alkylthio aremethylthio, pentylthio, dodecylthio and the like.

The term "aryloxy" as used herein means the monovalent moiety offormula:-

    aryl -- 0 --

wherein aryl is as before defined. Illustrative of aryloxy are phenoxy,naphthoxy, and the like.

The term "arylthio" is used herein to mean the monovalent moiety offormula:-

    aryl -- S --

wherein aryl is as defined above. Illustrative of arylthio arephenylthio, naphththio, and the like.

The term "alkylamino" is used herein to mean an amino group wherein onehydrogen atom has been replaced with an alkyl group as previouslydefined. Illustrative of alkylamino are methylamino, butylamino,dodecylamino, and the like.

The term "dialkylamino" is used to mean an amino group wherein bothhydrogen atoms have been replaced with alkyl groups as defined above.Illustrative of dialkylamino are groups such as dimethylamino,ethylhexylamino, didodecylamino and the like.

The term "acylamino" as used herein means the monovalent moiety offormula:- ##STR5## wherein R is alkyl as previously defined.

The term "lower alkyl" means alkyl as previously described having 1 to 4carbon atoms, inclusive, and the term "lower alkoxy" means alkoxy asdefined above having 1 to 4 carbon atoms, inclusive.

One skilled in the art will appreciate a variety of useful procedureswhich may be carried out by using the method of our invention. Forexample, natural prostaglandins are sought after for biological studiesand as therapeutics in the treatment of mammals for a variety ofclinical conditions. The extraction and recovery of naturalprostaglandins from animal tissues such as lung tissue, male accessorygenital glands and the like obtained from sacrificed animals is a costlyprocedure and any improvement of yields is a significant commercialfactor. By the method of our invention, effective amounts of compoundsof the formula (I) its pyridyl N-oxides and its pharmaceuticallyacceptable acid addition salts thereof are administered to the naturalprostaglandin-producing animal within a period of from 1 to 6 hoursprior to sacrifice. This results in enhanced yields of prostaglandinsrecovered by conventional and known methods of extraction.

By the method of our invention, mammal treatment procedures for avariety of clinical conditions responsive to prostaglandins areimproved. More specifically, those clinical conditions which are relatedto a prostaglandin deficiency or which respond to enhanced levels ofprostaglandins and in which there is an operative trigger mechanism forstimulation of prostaglandin production are advantageously responsive tothe method of our invention. Illustratively, some 13 differentprostaglandins, representing all four prostaglandin families are foundin mammalian seminal fluids. A correlation exists between lowprostaglandin levels (particularly of the PGE family) in seminal fluidsand male infertility; see, for example, "The Prostaglandins", Karim,Medical and Technical Pub. Co. Ltd., Oxford (1972) pp. 134-6. In thoseinstances wherein seminal fluid prostaglandins are produced by themammal, but in low quantity, production levels are raised by the methodof our invention. Thus, the method of our invention provides a method oftreating mammalian male infertility which comprises administering tosaid male an effective amount of a compound (I) or a pyridyl N-oxide ora pharmaceutically acceptable acid addition salt thereof.

To further illustrate the use of the method of our invention, it isknown that the prostaglandin PGE₂ is produced at the site of epidermalinjury in a mammal [see for example Anggard et al., Alza Conference onProstaglandins in Cellular Biology, Edited by Ramwell and Pharriss,Plenum Press, N.Y., N.Y. (1972), page 269.] The generally accepted roleof PGE₂ at the site of injury following, for example, burns, abrasions,surgery, penetration wounds and like epidermal injuries is to stimulateepidermal cell proliferation and keratin formation, thereby acceleratingwound healing. It should be further noted that the term "epidermalinjury" is broad enough in this context to include skin conditions suchas psoriasis wherein the PGE₂ stimulates production of cyclic AMP whichadditionally aids in overcoming the effects of the condition. By usingthe method of our invention, higher levels of PGE₂ are obtained overlong periods of time to accelerate the healing process. Thus, apreferred embodiment of the method of our invention comprises a methodof promoting the healing of epidermal injuries in a mammal whichcomprises administering to said mammal an effective amount of a compoundselected from those of the formula (I), pyridyl N-oxides thereof andpharmaceutically acceptable acid addition salts thereof. Surprisingly,although PGE₂ is a known mediary in the inflammatory process, the methodof our invention so employed does not produce a significant increase inthe manifestations generally associated with inflammation such as pain,edema, swelling and like inflammatory manifestations.

In another use, the method of our invention is employed advantageouslyto prevent or control atonic uterine bleeding. PGE₂ and PGF₂ α are bothproduced by the endometrium and blood platelets (upon aggregation). Insituations of post-partum hemorrhage due to an atonal uterus, theelevation of PGE₂ and PGF₂ α production by platelets at the site ofbleeding provides therapeutic levels of the two prostaglandinssufficient to render tone to the uterine muscle, thus causing sustainedcontractions of the uterus and controlling hemorrhage. The method of ourinvention therefore includes as an embodiment the prevention and controlof atonic uterine hemorrhage in a mammal which comprises administeringto the mammal an effective amount of a compound selected from those offormula (I), pyridyl N-oxides thereof and pharmaceutically acceptableacid addition salts thereof. Administration of the compound (I), itsN-oxides or its salts in this particular use is advantageously carriedout during a period of from 1 to 6 hours before an anticipatedhemorrhage to prevent the same, or immediately following the start ofhemorrhage. In the latter instance, control of bleeding generally occurswithin from 1 to about 3 hours of administration.

As mentioned above, PGF₂ α and PGE₂ are both produced by the mammalianblood platelet upon stimulation of synthesis by cell aggregation.Build-up of PGF₂ α and PGE₂ levels at the site of platelet aggregationare associated with inhibition of further platelet aggregation, therebyterminating the continued development of thrombi. By the method of ourinvention, one may terminate the development of thrombi earlier and morerapidly through enhanced levels of PGF₂ α and PGE₂ production. This isparticularly useful in the treatment and prevention of myocardialinfarcts, post-operative thrombosis, atherosclerosis, arteriosclerosisand like clinical conditions where the development of a thrombus isundesired. Thus, another embodiment of our invention comprises a methodof controlling the development of a thrombus in a mammal which comprisesadministering an effective amount of a compound selected from those offormula (I), pyridyl N-oxides thereof and pharmaceutically acceptableacid addition salts thereof, to said mammal.

DETAILED DESCRIPTION OF THE INVENTION

The compounds (I), pyridyl N-oxides thereof and pharmaceuticallyacceptable acid addition salts thereof are administered to the mammalsystemically and topically. Illustrative of methods of administrationare oral, parenteral and topical administrations. Oral and parenteraladministrations are preferred.

The effective amount administered is that quantity which brings about anincrease in the production levels of prostaglandins biosynthesized bythe subject mammal. The exact amount to be administered will depend upona number of factors such as, for example, the specific compound (I), itsN-oxide or salt, species of mammal, age, weight and physical conditionof the mammal, route of administration and in the instances wherein aspecific clinical condition is being treated by the method of theinvention, the nature of the condition. In general, prostaglandinproduction levels rise in direct proportion to the quantity of thecompound (I), its N-oxide or acid addition salt administered.

The exact dosage requirement in a given clinical situation may bedetermined by administration of a trial dose and observation of theprostaglandin production response by blood plasma analysis or byclinical response to the presence of prostaglandin. In general, aneffective amount to be administered is within the range of from about0.1 mg. to about 500 mg. per kilogram of body weight of the recipientmammal and preferably within the range of from about 5 mg. to about 50mg. per kilogram body weight. In general, the degree of response isrelated to dose, and higher doses produce faster and more completeclinical responses. In most instances, a single administration willeffect the desired response and bring about the result desired. In casessuch as in the treatment of epidermal injuries, however, it may bedesirable to repeat the administrations several times. In suchinstances, we have noted a decrease in degree of prostaglandinproduction response upon administrations subsequent to the firstadministration unless there is a resting period between administrations.Resting periods of from about 12 to about 24 hours betweenadministrations assure the highest prostaglandin production for a givendosage of the compounds (I), their N-oxides and pharmaceuticallyacceptable acid addition salts.

Although all mammalian tissues capable of producing prostaglandins areresponsive to the method of our invention, the most advantageousresponse is obtained from circulating blood platelets which produce PGE₂and PGF₂ α. The platelets produce larger quantities of theseprostaglandins and serve to meet therapeutic needs as described abovemost readily and conveniently. The method of our invention isparticularly advantageous in stimulating high yields of PGF₂ α from theproducing blood platelets.

Illustrative of the known compounds of formula (I) employed in themethod of our invention are 1-(2-pyridylmethyl)-3-phenylurea,1-(3-pyridylmethyl)-3-phenylurea and 1-(4-pyridylmethyl)-3-phenylurea[see Skinner et al., J. Org. Chem. 25, 2046-7 (1960)];1-(2-pyridylethyl)-3-phenylurea; 1-(4-pyridylethyl)-3-phenylurea,1-(2-pyridylethyl)-3-(4-methoxyphenyl)urea and1-(4-pyridylethyl)-3-(4-methoxyphenyl)urea [see Sheob et al., Indian J.Chem., 5, 145 (1967)]; 1-[2-methylpyridyl(methyl)]-3-phenylurea,1-[2-methylpyridyl(methyl)]-3-(2-chlorophenyl)urea,1-[2-methylpyridyl(methyl)]-3-(3-chlorophenyl)urea,1-[2-methylpyridyl(methyl)]-3-(4-chlorophenyl)urea and1-[2-methylpyridyl(methyl)]-3-(2,5-dichlorophenyl)urea [see Juby et al.,J. Med. Chem., 10, 491 (1967)];1-methyl-1-(2-pyridylmethyl)-3-phenylurea,1-methyl-1-(2-pyridylmethyl)-3-(4-methylphenyl)urea, 1-methyl-1-(2-pyridylmethyl)-3-(3-chlorophenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(3,4-dichlorophenyl)urea,1-methyl-1(2-pyridylmethyl)-3-(3-nitrophenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(3-trifluoromethylphenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(4-chloro-3-trifluoromethylphenyl)-urea,1-methyl-1-(2-pyridylmethyl)-3-(4-chlorophenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(3-fluorophenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(4-chloro-3-nitrophenyl)urea,1-methyl-1-(2-pyridylmethyl)-3-(3,4-dichlorophenyl)urea,1-methyl-1-(3-pyridylmethyl)-3-(4-chloro-3-fluorophenyl)-urea,1-methyl-1-(3-pyridylmethyl)-3-(4-chloro-3-nitrophenyl)urea,1-methyl-1-(3-pydridylmethyl)-3-(4-methylphenyl)urea,1-methyl-1-(3-pyridylmethyl)-3-(3,4-dimethylphenyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(3,4-dichlorophenyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(3-fluorophenyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(4-methylphenyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(3-nitrophenyl)urea, and1-methyl-1-(4-pyridylmethyl-3-(3-trifluoromethylphenyl)urea (see U.S.Pat. No. 3,700,678);1-(2-chlorophenyl)-3-(α-phenyl-4-pyridylmethyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(4-bromophenyl)urea,1-methyl-1-(4-pyridylmethyl)-3-(4-iodophenyl)urea,1-butyl-1-(4-pyridylmethyl)-3-methyl-3-(2-chlorophenyl)urea,1-(4-pyridylmethyl)-3-(3,4,5 -trimethoxyphenyl)urea,1-(2-pyridylmethyl)-3-(3,4,5-trimethoxyphenyl)urea,1-(4-methoxyphenyl)-3-(α-phenyl-4-pyridylmethyl)urea,1-(3,4,5-trimethoxyphenyl)-3-(α-phenyl-4-pyridylmethyl)-urea,1-methyl-1-(4-pyridylmethyl)-3-(4-methoxyphenyl)-urea,1-methyl-1-(4-pyridylmethyl)-3-(4-ethoxyphenyl)-urea,1-methyl-1-(4-pyridylmethyl)-3-(2-ethoxyphenyl)-urea,1-methyl-1-(3-pyridylmethyl)-3-(4-ethoxyphenyl)-urea, and1-methyl-1-(2-pyridylmethyl)-3-(4-ethoxyphenyl)-urea (see U.S. Pat. No.3,128,280).

The compounds (I) wherein R₄ is specifically hydrogen and R₆ and R₇ areother than amino, alkylamino or acylamino; i.e., a compound of theformula (VI); are readily prepared by the method set forth in U.S. Pat.No. 3,128,280. In general, the method comprises reacting an appropriateaminoalkylpyridine (IV) with an appropriate phenylisocyanate (V). Thereaction is conveniently illustrated by the schematic formula: ##STR6##wherein n, R₁, R₂, R₃ and R₅ are as defined above; R₂₂ and R₂₃ are eachselected from nitro, cyano, dialkylamino, alkylthio, arylthio, aryloxyand a group R₅ as defined previously.

The above illustrated reaction proceeds satisfactorily by adding theisocyanate reactant (V) to a solution of the aminoalkylpyridine (IV) inan inert organic solvent. An inert organic solvent is a solvent forreactant (IV) which does not react with components of the reactionmixture, or in any way interfere with the desired course of thereaction. Illustrative of inert organic solvents are tetrahydrofuran,dioxane, benzene, pyridine and the like. Generally, the above reactionis carried out at a temperature of from about 0° C. to 100° C. and iscomplete within 1 to 48 hours depending upon the nature of substituentsR₁, R₂, R₃, R₅, R₂₂ and R₂₃. Completion of the reaction may be observedby conventional analytical techniques such as by infrared spectralanalysis and thin-layer chromatography which will indicate thedisappearance of the isocyanate reactant. Upon completion of thereaction, the desired product compounds (IV) are readily separated fromthe reaction mixture by conventional methods such as, for example, bydistillation, crystallization, and like methods. For complete details ofthe above described method, see U.S. Pat. Nos. 3,128,280 and 3,700,678.

The starting aminoalkylpyridine compounds (IV) employed in the abovedescribed reaction are generally well known, and may be prepared by avariety of methods, see for example, Scully et al., supra., Shuman etal., J. Org. Chem., 27, 1970 (1962); Bobbitt et al., J. Org. Chem., 29,2298 (1964); Bower et al., J. Chem. Soc., 2834 (1955); Bruce et al., J.Am. Chem. Soc., 66, 2092 (1944); and Sam, J. Pharm. Sci., 56, 1202(1967).

A convenient method of preparing the aminoalkylpyridines (IV) wherein R₁and R₂ are other than acylamino groups is by reduction of thecorresponding amide compounds of formula: ##STR7## wherein m is aninteger of from 0 to 1 and R₃ is as defined above; A and B are eachselected from hydrogen, halogen, hydrocarbyl of 1 to 6 carbons,inclusive, alkoxy, alkylthio, nitro, amino, alkylamino, dialkylamino,and trihalomethyl. The methods of reduction are well known, see forexample, Tarbell et al., J. Am. Chem. Soc., 72, 2657 (1950); Uffer etal., Helv. Chim. Acta., 31, 1397 (1948); and Brown, Org. Reactions, Vol.6, J. Wiley and Sons, N.Y., N.Y., (1951), page 469.

The amides of formula (IVB) may be prepared by the method of Zymalkowskiet al., Arch. Pharm. 293, 47-53 (1960) which comprises heating thecorresponding pyridyl acetate with an appropriate amine. Representativeof the compounds (IVB) are 2-chloro-6-ethylthioisonicotinamide,N-butyl-2-ethylthioisonicotinamide, N-butyl-2,6-dichloroisonicotinamide,N-benzyl-4-pyridylacetamide, 2-chloro-6-methoxy-N-(α-methylphenylethyl)isonicotinamide, 2-pyridineacetanilide,N-cyclopropylisonicotinamide,2,6-dichloro-N-(cyclopropylmethyl)isonicotinamide,4'-phenoxynicotinanilide, 2'-phenylnicotinanilide,N-butyl-6-methylthiopicolinamide, N-cyclohexylpicolinamide,5'-methyl-4'-nitro-o-picolinanisidide, 4'-cyclohexylnicotinanilide,4,6-dichloropicolinamide, 4-ethoxypicolinamide, 5-ethylthiopicolinamide,N-1-naphthylisonicotinamide, 4'-chloroisonicotinanilide,p-isonicotinanisidine, 2'-chloro-4'-nitropicolinanilide,2',5'-diethoxy-4'-nitropicolinanilide and the like.

An alternative method of preparing the aminoalkylpyridines (IV) whereinR₃ is specifically hydrogen and the method for preparing compounds (IV)wherein R₁ or R₂ is an acylamino group is that disclosed by Scully etal., supra., which comprises reducing the corresponding nitrilecompounds of formula: ##STR8## wherein R₁, R₂ and m are as beforedefined. Representative of the compounds (IVC) are picolinonitrile,4-chloropicolinonitrile, 4,6-dimethylpicolinonitrile,4-phenylpicolinonitrile, 4-benzylpicolinonitrile,3-allylpicolinonitrile, 4-methoxypicolinonitrile,2,5-diethoxypicolinonitrile, 4-methylthiopicolinonitrile,3,5-dinitropicolinonitrile, 3,5-diaminopicolinonitrile,3-ethylaminopicolinonitrile, 3-diethylaminopicolinonitrile,4-acetylaminopicolinonitrile, 4-trifluoromethylpiconitrile and the like.

Those compounds (IV) wherein R₃ is as defined previously but other thanhydrogen and R₁ or R₂ are acylamino are prepared by N-acylating thecorresponding compound (IV) wherein the appropriate group R₁ or R₂ is anamino group. The method of N-acylation may be conventional such as, forexample, by reaction with an appropriate alkyl carboxylic acid, such asacetic acid, heptanoic acid, dineopentylacetic acid and the like.

The starting isocyanate compounds (V) employed in preparing thecompounds (I) are generally well known in the art as is theirpreparation by phosgenation of the corresponding primary amine.Illustrative of the compund (V) are phenylisocyanate,p-chlorophenylisocyanate, o-fluorophenylisocyanate,p-bromophenylisocyanate, 3,4-dichlorophenylisocyanate,4-bromo-2-chloro-phenylisocyanate, 4-iodophenylisocyanate,2,4,5-tribromophenylisocyanate, 4-bromo-3-fluorophenylisocyanate,o-methylphenylisocyanate, p-dodecylphenylisocyanate,2,4-dimethylphenylisocynate, 4-tert-butyl-2,6-diethylphenylisocyanate,2,4-ditert-butylphenylisocyanate, 2,6-diethylphenylisocyanate,p-cyclohexylphenylisocyanate, 3-chloro-2-methylphenylisocyanate,2-phenylphenylisocyanate, m-methoxyphenylisocyanate,p-ethoxyphenylisocyanate, 3,4-dimethoxyphenylisocyanate,4-butoxyphenylisocyanate, 5-chloro-2-methoxyphenylisocyanate,2-methoxy-5-methylphenylisocyanate, p-trifluoromethylphenylisocyanate,p-chlorophenylphenylisocyanate, m-nitrophenylisocyanate,3,5-dinitrophenylisocyanate, 3-nitro-o-tolylisocyanate,2-methoxy-4-nitrophenylisocyanate, 2-bromo-4-nitrophenylisocyanate,2,6-dichloro-4-nitrophenylisocyanate, p-cyanophenylisocyanate,3-chloro-4-cyanophenylisocyanate, o-phenoxyphenylisocyanate,3-chloro-4-(methylthio)phenylisocyanate,3-chloro-4-(ethylthio)phenylisocyanate, o-(phenylthio)phenylisocyanate,p-(diethylamino)phenylisocyanate and the like.

The compounds (I) wherein R₃ is specifically hydrogen and R₁ and R₂ areas previously defined but other than amino, alkylamino or acylamino;i.e., compounds of formula (VII) are also prepared by the same generalmethod described in U.S. Pat. Nos. 3,128,280 and 3,700,678 employing asthe reactants, however, a pyridylalkylisocyanate (VIII) and an aniline(IX). The reaction is illustrated schematically by the formula: ##STR9##wherein n, R₄, R₅, R₆ and R₇ are as previously defined; R₂₄ and R₂₅ areeach selected from hydrogen, halogen, hydrocarbyl of 1 to 6 carbons,inclusive, alkoxy, alkylthio, nitro, dialkylamino and trihalomethyl.

Pyridylalkylisocyanates of formula (VIII) are prepared by phosgenationof the corresponding primary pyridylalkylamine such as those within thescope of formula (IV) previously described. The techniques ofphosgenating primary amines to prepare corresponding isocyanates arewell known, see for example Polyurethanes Chemistry and Technology; PartI, Saunders and Frisch, Interscience, N.Y., N.Y. (1962), pp. 18-29.Starting aniline compounds (IX) used in the above described reaction aregenerally well known and are represented by aniline, p-chloroaniline,2,5-dibromoaniline, 3,4,5-trichloroaniline, m-toluidine,3,5-dibutylaniline, 3-allylaniline, p-phenylaniline, p-benzanilide,m-phenetidine, 3,4,5-trimethoxyaniline, m-dichloromethylaniline,p-(p-chlorophenyl)aniline, p-nitroaniline, m-cyanoanilide,p-phenylenediamine, p-acetylaminoaniline, o-methylaminoaniline,o-dimethylaminoaniline, 2,5-dimethylthioaniline, p-phenylthioaniline,p-phenoxyaniline, o-(2-chloroethyl)aniline, 4-methylthio)aniline,3-(ethylthio)-4-(methylthio)aniline, 4-bromo-2-chloroaniline,2-bromo-4,6-dinitroaniline, 2-bromo-4-methylaniline,2-bromo-4-nitroaniline, 3-chloro-o-anisidine,5-chloro-2,4-dimethoxyaniline, 4-fluoro-3-nitroaniline,p-(2,2,2-trichloroethyl)aniline, N-methyl-aniline, N-butyl-aniline;N-cyclohexyl-aniline, N-phenyl-aniline, N-benzyl-aniline,N-(p-nitrophenyl)-aniline, N-(o-methylphenyl)-aniline,N-biphenyl-aniline, N-(p-phenoxy-phenyl)-aniline and the like.

Those compounds (I) wherein R₁, R₂, R₆ and R₇ are specifically selectedfrom amino, alkylamino, and acylamino are prepared from thecorresponding compounds (I) wherein R₆ and/or R₇ are nitro groups. Thus,by conventional methods of reduction [see for example the method ofPietra, Ann. Chim., 45, 850 (1955)] the nitro substituent group isreduced to an amino group; and by conventional methods well known in theart, such as by reaction with an appropriate alkyl halide of formula:

    alkyl--X

wherein X represents halogen the primary amino groups may be convertedto alkylamino groups [see for example the method of Johnstone et al., J.Chem. Soc., (C), 2223 (1969)]. When desired, conversion of the R₁, R₂,R₆ and/or R₇ substituent amino groups to an acylamino group is alsocarried out by conventional and known methods, such as by reaction ofsaid amino group with an appropriate acid anhydride or acyl halide ofthe formula: ##STR10## where X and alkyl are as defined previously.

An alternate method of preparing the compounds (I) is also described inU.S. Pat. 3,128,280. In general, the alternate method comprises reactingan aminoalkylpyridine (IV) as previously described with an appropriateN-phenyl carbamoyl chloride (X) according to the schematic formula:##STR11## wherein n, R₁, R₂, R₃, R₄, R₅, R₆, and R₇ are as definedabove.

In the above described alternate method, the starting carbamoylreactants (X) are prepared by conventional phosgenation of thecorresponding aniline (IX) supra.; see for example, the method of K.Palat et al., Chem. Listy, 51, 563 (1957) and of German Patent 870,097.

The pyridyl N-oxides of the compounds (I), i.e., compounds of theformula:- ##STR12## corresponding to the compounds (I) and thepharmaceutically acceptable acid addition salts thereof wherein R₁, R₂,R₃, R₄, R₅, R₆, R₇ and n have the meanings previously ascribed to them,are also novel compounds and are useful for the same purposes and in thesame manner as the nonoxides of formula (I).

The pryidyl N-oxides (XI) are prepared by N-oxidation of thecorresponding compound (I). Such oxidations are well known and aregenerally carried out by reacting the compound (I) with an excess molarproportion of an oxidizing agent such as hydrogen peroxide. See, forexample, the procedure disclosed by E. Ochiai, Aromatic Amino Oxides,Elsevier Publishing Company, New York, p. 25 (1967).

The pharmaceutically acceptable acid addition salts of the compounds (I)and (XI) may be used for the same purposes as the corresponding freebase compounds, and in the same manner. They are readily prepared byreacting the free base with a stoichoimetric proportion of anappropriate acid. The method is well known to those skilled in the artand may be carried out in aqueous or nonaqueous media such as ethanol,ether, ethyl acetate and the like. Illustrative of pharmaceuticallyacceptable acid addition salts are those formed upon reaction of thefree base compound (I) or compound (XI) with hydrochloric acid,hydrobromic acid, sulfuric acid, phosphoric acid, acetic acid, lacticacid, citric acid, succinic acid, benzoic acid, salicylic acid, pamoicacid, cyclohexanesulfamic acid and the like.

This invention relates also to pharmaceutical dosage unit forms forsystemic effects (oral, parenteral and rectal administration) andtopical administration which are useful in improving the production ofendogenous prostaglandins by mammals, including humans. The term "dosageunit form" as used in this specification and in the claims refers tophysically discrete units suitable as unitary dosaged for mammaliansubjects, each unit containing a predetermined quantity of the essentialactive ingredient, i.e., a compound of formula (XI); or a compound ofthe formula (I) wherein it is provided that when R₁ and R₂ are bothselected from hydrogen and alkyl, said compound (I) is selected fromthose wherein R₇ is selected from cycloalkyl, aryl, aralkyl, alkenyl,cyano, amino, acylamino, alkylamino, dialkylamino, arylthio, alkylthioand those wherein R₄ is selected from cycloalkyl, aralkyl, aryl and arylsubstituted with a group selected from halogen, lower alkoxy,hydrocarbyl, or one to six carbon atoms, inclusive, nitro orpharmaceutically acceptable acid addition salts thereof, calculated toproduce the desired effect in combination with the requiredpharmaceutical means which adapt said ingredient for systemicadministration. Examples of dosage unit forms in accordance with thisinventon are tablets, capsules, orally administered liquid preparationsin liquid vehicles, sterile preparations in liquid vehicles, sterilepreparations in liquid vehicles for intramuscular and intravenousadministration, rectal suppositories, sterile dry preparations for theextemporaneous preparation of sterile injectable preparations in aliquid vehicle, ointments, lotions, pastes, jellies, sprays, aerosols,and the like. Solid diluents or carriers for the solid oralpharmaceutical dosage unit forms are selected from the group consistingof lipids, carbohydrates, proteins and mineral solids, for example,starch, sucrose, kaolin, dicalcium phosphate, gelatin, acacia, cornsyrup, corn starch, talc and the like. Capsules, both hard and soft, areformulated with conventional diluents and excipients, for example,edible oils, talc, calcium carbonate, calcium stearate and the like.

Liquid preparations for oral administration are prepared in water oraqueous solutions which advantageously contain suspending agents suchas, for example, carboxymethylcellulose, methylcellulose, acacia,polyvinyl pyrrolidone, polyvinyl alcohol and the like. In the instanceof injectable forms they must be sterile and must be fluid to the extentthat easy syringeability exists. Such preparations must be stable underthe conditions of manufacture and storage, and oridinarily contain, inaddition to the basic solvent or suspending liquid, preservatives in thenature of bactericidal and fungicidal agents, for example parabens,chlorobutanol, benzyl alcohol, phenol, thimerosal and the like. In manycases it is preferable to include isotonic agents, for example sugars orsodium chloride. Carriers and vehicles include vegetable oils, ethanoland polyols, for example glycerol, propylene glycol, liquid polyethyleneglycol and the like. Any solid preparations for subsequentextemporaneous preparation of sterile injectable preparations aresterilized, preferably by exposure to a sterilizing gas such as, forexample, ethylene oxide. The aforesaid carriers, vehicles, diluents,excipients, preservatives, isotonic agents and the like constitute thepharmaceutical means which adapt the preparations for systemicadministration.

For topical use, this compound can be formulated in a pharmaceuticalcarrier suitable for application to affected areas of the skin, eyes,ears or mucous membranes. Accordingly, the compositions of thisinvention include those pharmaceutical forms in which the medication isapplied externally for direct contact with the surface to be treated.Conventional pharmaceutical forms for this purpose include ointments,creams, lotions, solutions, suspensions, pastes, jellies, sprays andaerosols (e.g., for oral or nasal use or on the skin), drops (e.g., foruse in the eyes or ears), powders (e.g., for use on the skin) and thelike. In preparing the desired topical formulations of the novelcompound of this invention, various additives, diluents and adjuvantscan be utilized. These illustratively include water, surfactants (e.g.,polysorbate 80 and polyoxethylene sorbitan monostearate), emulsifiers(e.g., glyceryl monostearate-diethylaminoethyl alkyl amide phosphate,isopropyl myristate and cetyl alcohol), alcohols (e.g., ethanol andisopropanol), lower alkyl diols (e.g., 1,3-butanediol, 2,3-butanediol,1,2-propanediol, 1,3-propanediol), glycols (e.g., propylene glycol,glycerol, sorbitol), ointment-type bases (e.g., spermaceti, Carbowaxes,beeswax, petrolatum, lanolin), higher fatty acids and alcohols (e.g.,stearic acid, stearyl alcohol, cetyl alcohol, palmitic acid), liquidparaffin and vegetable oils (e.g., peanut oil, castor oil),preservatives such as sorbic acid, parabens, chlorocresol, benzalkoniumchloride) and solid diluents (e.g., lactose, starch, bentonite, talc).

A rectal suppository can be employed to deliver the active compoundwhere the mammal cannot be treated conveniently by means of other dosageforms, such as orally, as in the case of young children or debilitatedpersons. The active compound can be incorporated into any of the knownsuppository bases by methods known in the art. Examples of such basesinclude cocoa butter, polyethylene glycols (Carbowaxes), polyethylenesorbitan monostearate, and mixtures of these with other compatiblematerials to modify the melting point or dissolution rate. These rectalsuppositories can weigh from about 1 to 2.5 Gm.

The pharmaceutical dosage unit forms are prepared in accordance with thepreceding general description to provide from about 10 to about 1500 mg.of the essential active ingredient per dosage unit form with preferably100 to 1000 mg. in the oral and parenteral forms. With regard to topicalforms, the dosage is from about one to about fifteen per weight percentof the suppository.

The following examples describe the manner and process of making andusing the invention, and set forth the best mode contemplated by theinventors of carrying out the invention but are not to be construed aslimiting.

EXAMPLE 1

1,1-Diphenyl-3-(3-pyridylmethyl)urea

An appropriate reaction vessel is charged with 4.32 gms. (0.04 mole) of3-aminomethylpyridine, 4.5 gms. (0.04 mole) of triethylamine and 100 ml.of tetrahydrofuran. To the resulting mixture, 9.27 gms. (0.04 mole) ofdiphenylcarbamoyl chloride is added with stirring. Stirring ismaintained for about 24 hours. after which the mixture is diluted withwater to give a total volume of 1 liter. A solid separates which isremoved, washed with water and dried. Upon recrystallization of thesolid from ethanol there is obtained 5.53 gms. (47 percent of theory) of1,1-diphenyl-3-(3-pyridylmethyl)urea in the form of tan crystals, m.p.142.7° C.

Similarly, following the above procedure, but replacing thediphenylcarbamoyl chloride as used therein with an equal molarproportion of the following compounds of the formula (X);methyl(P3-nitro-p-anisoyl)carbamoyl chloride,methyl(3-nitro-p-tolyl)carbamoyl chloride, and methyl(p-tolyl)carbamoylchloride, respectively, there is obtained1-methyl-3-(3-nitro-p-anisoyl)-3-(3-pyridylmethyl)urea,1-methyl-1-(3-nitro-p-tolyl)-3-(3-pyridylmethyl)urea, and1-methyl-1-(p-tolyl)-3-(3-pyridylmethyl)urea, respectively, andreplacing the diphenylcarbamoyl chloride as used therein with an equalmolar proportion of the following compounds of the formula (X);cyclohexylphenylcarbamoyl chloride, benzylphenylcarbamoyl chloride,(p-nitrophenyl)phenylcarbamoyl chloride o-tolylphenylcarbamoyl chloride,biphenyllylphenylcarbamoyl chloride, and phenoxyphenylphenylcarbamoylchloride, respectively, all of which may be prepared by phosgenation ofthe corresponding amine of formula (IX), supra., [see the methods ofSlocombe et al., J.A.C.S., 72, 1888 (1950) and Raiford et al., J. Org.Chem., 5, 306 (1940)]; there is obtained1-methyl-1-cyclohexylphenyl-3(3-pyridylmethyl)urea,1-methyl-1-benzylphenyl-3-(3-pyridylmethyl)urea,1-methyl-1-[(-p-nitrophenyl)phenyl]-3-(3-pyridylmethyl)urea,1-methyl-1(o-tolylphenyl)-3-(3-pyridylmethyl)urea,1-methyl-1-(biphenylylphenyl)-3-(3-pyridylmethyl)urea, and1-methyl-1-[(phenoxyphenyl)phenyl]-3-(3-pyridylmethyl)urea,respectively.

EXAMPLE 2

1,1-Diphenyl-3-(4-pyridylmethyl)urea

Following the procedure of Example 1, supra., but replacing the3-aminomethylpyridine as used therein with 5.41 gms. (0.05 mole) of4-aminomethylpyridine, increasing the proportion of triethylamine to5.05 gms. (0.05 mole) and increasing the proportion ofdiphenyl)carbamoyl chloride to 11.58 gms. (0.05 mole) there is obtained2.60 gms. (17 percent of theory) of 1,1-diphenyl-3-(4-pyridylmethyl)ureain the form of a pale yellow powder, m.p. 174.1° C.

Similarly, following the above procedure but replacing the4-aminomethylpyridine as used therein with an equal molar proportion ofthe following compounds of formula (IV):

4-aminomethyl-2-chloropyridine,

4-aminomethyl-2,5-dimethylpyridine,

4-aminomethyl-3-allylpyridine,

4-aminomethyl-3-methoxypyridine,

4-aminomethyl-3-phenylpyridine,

4-aminomethyl-3-ethylthiopyridine,

3-aminomethyl-2,5-dinitropyridine,

3-aminomethyl-2,5-diaminopyridine,

2-aminomethyl-4-methylaminopyridine,

2-aminomethyl-4-diethylaminopyridine,

2-aminomethyl-4-acetylaminopyridine, and

2-aminomethyl-4-(trifluoromethyl)pyridine,

respectively, [all of which are prepared by reduction of the appropriatecompound (IVC), method of Sculley et al., supra.)], there is obtained

1,1-diphenyl-3-[4-(2-chloropyridyl)methyl]urea,

1,1-diphenyl-3-[4-(2,5-dimethylpyridyl)methyl]urea,

1,1-diphenyl-3-[4-(3-allylpyridyl)methyl]urea,

1,1-diphenyl-3-[4-(3-methoxypyridyl)methyl]urea,

1,1-diphenyl-3-[4-(3-phenylpyridyl)methyl]urea,

1,1-diphenyl-3-[4-(3-ethylthiopyridyl)methyl]urea,

1,1-diphenyl-3-[3-(2,5-dinitropyridyl)methyl]urea,

1,1-diphenyl-3-[3-(2,5-diaminopyridyl)methyl]urea,

1,1-diphenyl-3-[2-(4-methylaminopyridyl)methyl]urea,

1,1-diphenyl-3-[2-(4-diethylaminopyridyl)methyl]urea,diethylaminopyridyl)methyl]urea,

1,1-diphenyl-3-[2-(4-acetylaminopyridyl)methyl]urea,

1,1-diphenyl-3-[2-(4-trifluoromethylpyridyl)methyl]urea.

EXAMPLE 3

1,1-Diphenyl-3-(2-pyridylethyl)urea

Following the procedure of Example 1, supra., but replacing the3-aminomethylpyridine as used therein with 3.66 gms. (0.03 mole) of2-aminoethylpyridine, decreasing the proportion of triethylamine as usedtherein to 3.03 gms. (0.03 mole) and decreasing the proportion ofdiphenylcarbamoyl chloride as used therein to 6.95 gms. (0.03 mole)there is obtained 5.96 g. (63 percent of theory) of1,1-diphenyl-3-(2-pyridylethyl)urea in the form of colorless crystals,m.p. 109.1° C.

EXAMPLE 4

1,1-Diphenyl-3-methyl-3-(2-pyridylethyl)urea

An appropriate reaction vessel is charged with 6.8 gms. (0.05 mole) of2-methyl-aminoethylpyridine, 5.05 gms. (0.05 mole) of triethylamine and100 ml. of tetrahydrofuran. To the resulting mixture, 11.58 gms. (0.05mole) of diphenylcarbamoyl chloride is added with stirring. Afterstirring at room temperature for 24 hours, the mixture is diluted withwater to obtain a mixture having a volume of 1 liter. The dilute mixtureis distilled to yield an oil which is1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea.

Similarly, following the above procedure but replacing the2-methylaminoethylpyridine as used therein with an equal molarproportion of

2-(β -cyclohexylaminoethyl)pyridine,

2-(β -phenylaminoethyl)pyridine,

2-(β -benzylaminoethyl)pyridine, and

2-[β-(p-methoxyphenylamino)ethyl]pyridine

respectively, all of which may be prepared by reduction of thecorresponding amide of Formula (IVB) (method of Tarbell et. al.,supra.,), there is obtained

1,1-diphenyl-3-cyclohexyl-;

1,1-diphenyl-3-phenyl-;

1,1-diphenyl-3-benzyl-; and

1,1-diphenyl-3-(p-methoxyphenyl)-3-(2-pyridylethyl)-urea, respectively.

EXAMPLE 5

To a solution of 3.25 gms. (0.03 mole) of 4-aminomethylpyridine in 100ml. of tetrahydrofuran there is slowly added with stirring 5.70 gm.(0.03 mole) of p-diethylaminophenylisocyanate. The resulting mixture isallowed to stand for about 24 hours at room temperature and then it isrefluxed for 10 minutes. Solvent is then stripped to give a residuewhich is 1-(4-pyridylmethyl)-3-(p-diethylaminophenyl)urea.

Similarly, following the above procedure, but replacing thep-diethylaminophenylisocyanate as used therein with equal molarproportions of

p-cyclohexylphenylisocyanate,

p-phenylphenylisocyanate,

p-benzylphenylisocyanate,

m-allylphenylisocyanate,

m-cyanophenylisocyanate,

m-methoxyphenylisocyanate,

p-trifluoromethylphenylisocyanate,

m-diethylaminophenylisocyanate,

p-methylthiophenylisocyanate

p-phenylithiophenylisocyanate, and

p-phenoxyphenylisocyanate, respectively, there is obtained

1-(4-pyridylmethyl)-3-(p-cyclohexylphenyl)urea,

1-(4-pyridylmethyl)-3-(p-biphenyl)urea,

1-(4-pyridylmethyl)-3-(p-benzylphenyl)urea,

1-(4-pyridylmethyl)-3-(m-allylphenyl)urea,

1-(4-pyridylmethyl)-3-(m-cyanophenyl)urea,

1-(4-pyridylmethyl)-3-(m-methoxyphenyl)urea,

1-(4-pyridylmethyl)-3-(p-trifluoromethylphenyl)-urea,

1-(4-pyridylmethyl-3-(m-diethylaminophenyl)urea,

1-(4-pyridylmethyl-3-(p-methylthiophenyl)urea,

1-(4-pyridylmethyl)-3-(p-phenylthiophenyl)urea, and

1-(4-pyridylmethyl)-3-(p-phenoxyphenyl)urea, respectively.

EXAMPLE 6

1-(p-aminophenyl)-3-(4-pyridylmethyl)urea.

To a mixture of 5.72 gms. (0.02 mole) of1-(p-nitrophenyl)-3-methyl-3methyl-3-(4-pyridylmethyl)urea (see U.S.Pat. No. 3,700,678), 200 ml. of ethanol and 65 ml. of hydrazine hydratethere is added with stirring 0.5 gms. of 5 percent palladium-on-carbonin 50 ml. of ethanol. The resulting mixture is allowed to standovernight at room temperature and then is refluxed for two to threehours. The hot reaction mixture is then filtered and the filtrateevaporated to remove solvent. The residue is1-(p-aminophenyl)-3-methyl-3-(4-pyridylmethyl)urea.

EXAMPLE 7

1-(p-acetamidophenyl)-3-methyl-3-(4-pyridylmethyl)urea.

To a chilled (circa 0° C.) solution of 5.12 gms. (0.02 mole) of1-(p-aminophenyl)-3-methyl-3-(4-pyridylmethyl)urea (Example 6., supra.)in 75 ml. of pyridine there is added dropwise 1.48 gms. (0.02 mole) ofacetyl chloride with stirring, while maintaining the temperature of thereaction mixture at circa 0° C. Stirring is continued for 30 minutes andthen the reaction mixture is allowed to stand at room temperatureovernight. Solvent is stripped and the residue suspended in water. Uponremoval of the water there is obtained1-(p-acetamidophenyl)-3-(4-pyridylmethyl)urea.

EXAMPLE 8

1-(p-ethylaminophenyl)-3-methyl-3-(4-pyridylmethyl)urea

To 2.89 gms. (0.01 mole) of1-(p-trifluoroacetamidophenyl)-3-methyl-3-(4-pyridylmethyl)urea[prepared by reacting 1-(p-aminophenyl)-3-methyl-3-(4-pyridylmethyl)urea (Example 6., supra.) with trifluoroaceticanhydride (method of Hickenbottom, Reactions of Organic Compounds,Longmans, London, 1963)] there is added 6.24 gms. (0.04 mole) of ethyliodide in 50 ml. of dry acetone. The acetone is then stripped and theresidue added to 50 ml. of water. The aqueous mixture is warmed toreflux for about 30 minutes and then allowed to stand overnight. Themixture is then stripped of water to give1-(p-ethylaminophenyl)-4-methyl-3-(4-pyridylmethyl)urea.

EXAMPLE 9

1,1-Diphenyl-3-methyl-3-(2-pyridylethyl)urea hydrochloride

The 1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea obtained in Example 4,supra., is dissolved in 150 ml. of ethanol. To the solution there isadded sufficient concentrated hydrochloric acid to acidify the solutionto a pH of circa 5, and then the resulting solution is chilled,whereupon a solid precipitates. The precipitate is separated, washedwith cold ethanol and dried to give 13.36 gms. (73 percent of theory)based upon starting 2-methylaminoethylpyridine of1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea hydrochloride in the formof white crystals.

Similarly, following the above procedure but replacing the1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea as used therein with anequal molar proportion of any of the compounds prepared according toExamples 1-8 supra., the corresponding hydrochloride salt is obtained.

EXAMPLE 10

1-(4-pyridylmethyl)-3-phenylurea-N-oxide

To an appropriate reaction vessel there is charged 11.35 gms. (0.05mole) of 1-(4-pyridylmethyl)-3-phenylurea dissolved in 100 ml. ofglacial acetic acid. To the solution there is added 7.5 ml. of 30percent hydrogen peroxide and the resulting solution is allowed to standovernight at room temperature. At the end of this period, the mixture isheated circa. 60° C. - 80° C. for about four hours. The mixture is thenevaporated to dryness and the residue mixed with water. The resultingmixture is evaporated to remove water, leaving a viscous liquid whichsolidifies upon standing. The solid is suspended in 200 ml. of water andfiltered. The filtrate is neutralized to a pH of 7 with sodium carbonatewhereupon a precipitate appears. The precipitate is separated, washedwith water and crystallized from absolute ethanol to give 2.11 gms. (18percent of theory) of 1-(4-pyridylmethyl)-3-phenylurea-N-oxide in theform of fine white crystals, m.p. 174.1° C.

EXAMPLE 11

1-(2-nitrophenyl)-3-(2-pyridylethyl)urea-N-oxide

Following the procedure of Example 10., supra., but replacing the1-(4-pyridylmethyl)-3-phenylurea as used therein with 14.30 gms. (0.05mole) of 1-(2-nitrophenyl)-3-(2-pyridylethyl)urea, there is obtained9.39 gms. (62 percent yield) of1-(2-nitrophenyl-3-(2-pyridylethyl)urea-N-oxide in the form of brightyellow feathery crystals, m.p. 182.0° C.

EXAMPLE 12

1,1-Diphenyl-3-(2-pyridylethyl)urea-N-oxide

Following the procedure of Example 10, supra., but replacing the1-(4-pyridylmethyl)-3-phenylurea as used therein with 15.85 gms. (0.05mole) of 1,1-diphenyl-3-(2-(2-pyridylethyl)urea (Example 3, supra.)there is obtained 6.88 gms. (42 percent of theory) of1,1-diphenyl-3-(2-pyridylethyl)urea-N-oxide in the form of gray-browncrystals, m.p. 139.4° C.

Similarly, repeating the above procedure but replacing the1,1-diphenyl-3-(2-pyridylethyl)urea as used therein with an equal molarproportion of any compound of the formula (I) or acid salt thereof suchas those prepared according to Examples 1 to 9, supra., and the acidaddition salts thereof, the corresponding N-oxide is obtained.

The following examples illustrate the compositions and uses of thecompounds of the invention and the method of the invention.

EXAMPLE 13

Tablets

One thousand tablets for oral use, each containing 250 mg. of1,1-diphenyl-3-(3-pyridylmethyl)urea as the essential active ingredientare prepared from the following ingredients:

    ______________________________________                                        1,1-diphenyl-3-(pyridylmethyl)urea                                                                    250 gms.                                              lactose                 200 gms.                                              microcrystalline cellulose N.F.                                                                       50 gms.                                               starch                  5 gms.                                                magnesium stearate powder                                                                             1 gm.                                                 ______________________________________                                    

The ingredients are thoroughly mixed and slugged. The slugs are brokendown by forcing through a screen and the resulting granules are thencompressed into tablets.

These tablets are useful in controlling atonic uterine hemorrhage inadult humans when given at a dose of 1 to 6 tablets. High blood levelsof PGF₂ α and PGE₂ are observed for from 6 to 8 hours afteradministration.

The tablets are also useful for treating male mammals for infertilitywhen 1 to 3 tablets are given 3 to 4 times a week.

EXAMPLE 14

Capsules

One thousand two-piece hard gelatine capsules for oral use, each capsulecontaining 250 mg. of 1,1-diphenyl-3-(2-pyridylethyl)urea (Example 3,supra., are prepared from the following ingredients:

    ______________________________________                                        1,1-diphenyl-3-(2-pyridylethyl)urea                                                                   250 gms.                                              lactose                 200 gms.                                              talc                    25 gms.                                               magnesium stearate      2 gms.                                                ______________________________________                                    

The finely powdered materials are mixed thoroughly, then filled intohard gelatin capsules of appropriate size. The capsules are given toadult humans suffering from burns at a dose of 1 to 3 capsules given 3to 14 times a week, resulting in an acceleration of healing andepidermal proliferation.

EXAMPLE 15

Aqueous solution

An aqueous oral preparation containing in each teaspoonful (5 ml.) 500mg. of essential active ingredient is prepared from the following:

    ______________________________________                                        1,1-diphenyl-3-methyl-3-(2-pyridyl-                                            ethyl)urea hydrochloride                                                                           500        gms.                                          (Example 5, supra.)                                                          glycerin              2000       ml.                                          tragacanth powder     50         gms.                                         propylparaben         3          gms.                                         sucrose               6.5        gms.                                         orange oil flavor     5          gms.                                         deionized water q.s.  5000       ml.                                          ______________________________________                                    

The above oral preparations may be given to adult humans at a dose of 1to 4 teaspoons 3 to 14 times weekly to accelerate the healing ofepidermal wounds.

EXAMPLE 16

Injectable

A sterile suspension suitable for intramuscular injection and containingin each milliliter 250 mg. of1-(4-pyridylmethyl)-3-(2,5-dimethylphenyl)urea is prepared from thefollowing ingredients:

    ______________________________________                                        1-(4-pyridylmethyl)-3-(2,5-dimethyl-                                           phenyl)urea          250        gms.                                         benzyl benzoate       200        ml.                                          methylparaben         1.5        gms.                                         propylparaben         0.5        gms.                                         cottonseed oil q.s.   1000       ml.                                          ______________________________________                                    

The above sterile injectable is useful in controlling the developementof thrombi following saphenectomy when given at a dose of 1 to 4 ml.administered 2 to 6 hours prior to said saphenectomy.

EXAMPLE 17

Suppository

One thousand suppositories, each weighing 4.0 gms. and containing 500mg. of 1,1-diphenyl-3-(2-pyridylethyl)urea-N-oxide (Example 10, supra.)as the essential active ingredient are prepared from the followingingredients:

    ______________________________________                                        1,1-diphenyl-3-(2-pyridylethyl)-                                               urea-N-oxide           500     gms.                                          propylene glycol        2000    gms.                                          polyethylene glycol 4000                                                                              1000    gms.                                          polyethylene glycol 400 500     gms.                                          ______________________________________                                    

The 1,1-diphenyl-3-(2-pyridylethyl)urea N oxide is added to thepropylene glycol and the mixture milled until uniformly dispersed. Thepolyethylene glycol 4000 and polyethylene glycol 400 are melted togetherand the propylene glycol dispersion added. The suspension is poured intomolds and allowed to cool and solidify.

These suppositories are useful for controlling development of thrombi inmammals when given rectally at a dose of 1 suppository 3 to 7 times aweek.

EXAMPLE 18

Various compounds of the formula (I) are admixed with water andadministered orally to groups of 5 male Carworth rats (weighing 250-275gms. each) at a dosage of 60 mg. per kilogram of body weight. The ratsare prepared by fasting overnight (16 hours) prior to administration.About 3 hours after administration, tails are clipped and the rats bled.5 ml. of blood is collected in citrated syringes (0.1 ml. of 3.8 percentw/v sodium citrate per ml. of whole blood). The collected blood iscentrifuged at 900 rpm for 15 minutes and the platelet rich plasmaseparated and pooled for each group of 5 rats. For each 1.0 mls. ofpooled plasma there is added 0.5 ml. of 0.15M sodium phosphate buffer(pH 7.4). The resulting mixture is allowed to stand at room temperaturefor 30 minutes and then 0.5 mls. of sodium fluoride (4 mgs./ml. aqueoussolution) is added. The mixture is then incubated at 37° C. for sixtyminutes, cooled under running tap water and centrifuged at 2500 rpm for20 minutes. The supernatant solution is separated and analyzed for PGF₂α concentration by the method of Kirton et al., Biochemical andBiophysical Res. Comm. Volumn 47, 903 (1972).

The compounds employed and the results obtained are given in Table Ibelow. Group A does not represent the invention but is a control groupof 5 rats which did not receive an administration of a compound (I).

                  TABLE I                                                         ______________________________________                                                                   Concentration                                                Compound (I)     of PGF.sub.2 α Found                         Group     Administered     (ng./ml.)                                          ______________________________________                                        A (Control)                                                                             None             33.8 ±  4.2                                     B         1-(4-pyridylmethyl)-                                                          3-(4-chlorophenyl)urea                                                                         45.8 ±  4.3                                     C         1-(4-pyridylmethyl)-                                                          3-(2-fluorophenyl)urea                                                                         157.2 ± 14.6                                    ______________________________________                                    

Similarly, repeating the above procedure but replacing the compounds offormula (I) as used therein with any other compounds of the formula (I),or of the formula (XI) and the pharmaceutically acceptable acid additionsalts thereof such as for example:

1-(2-pyridylmethyl)-3-phenylurea,

1-(2-pyridylethyl)-3-(4-methoxyphenyl)urea,

1-[2-(3-methyl)pyridyl-(methyl)]-3-phenylurea,

1-methyl-1-(2-pyridylmethyl)-3-phenylurea,

1-methyl-1-(2-pyridylmethyl)-3-(3-nitrophenyl)urea

1-methyl-1-(2-pyridylmethyl)-3-(3-trifluoromethylphenyl)urea,

1-methyl-1-(3-pyridylmethyl)-3-(3,4-dimethylphenyl)urea,

1-methyl-1-(4-pyridylmethyl)-3-(4-ethoxy-phenyl)urea,

the like and such as those prepared according to Example 1-12, supra.,similar observations of increased prostaglandin production are made.

A further group of compounds of the invention are those compounds ofFormula I wherein R₁, R₅ and R₆ are hydrogen; R₂ is selected from thegroup consisting of hydrogen, halogen, alkyl of one to four carbonatoms, inclusive, alkoxy of one to four carbon atoms, inclusive, andtrifluoromethyl; R₃ and R₄ are the same or different and are selectedfrom the group consisting of hydrogen, alkyl of one to four carbonatoms, inclusive, and phenyl; R₇ is selected from the group consistingof hydrogen, halogen, alkyl of one to four carbon atoms, inclusive,alkoxy of one to four carbon atoms, inclusive, trifluoromethyl, andnitro; n is one or two; provided that when R₇ is chloro, the pyridinering moiety is attached to the alkylene at the 4-carbon position; andfurther provided that when R₂ is hydrogen or alkyl of one to four carbonatoms, inclusive, then R₇ is trifluoromethyl or nitro and R₄ is phenyl.

The N-oxides of the above-identified group are also within the scope ofthis invention. The groupings of compounds are useful in the same manneras the previous generic groupings and are formulated into likecompositions.

We claim:
 1. A compound selected from those of formula: ##STR13## and apharmaceutically acceptable acid addition salt thereof wherein R₁ and R₂are each selected from the group consisting of hydrogen, halogen, alkylof one to six carbon atoms, inclusive, cycloalkyl of three to six carbonatoms, inclusive, alkenyl of two to six carbon atoms, inclusive, phenyl,alkoxy of one to twelve carbon atoms, inclusive, nitro, amino,alkylamino with alkyl of one to twelve carbon atoms, inclusive,dialkylamino with each alkyl having one to twelve carbon atoms,inclusive, acylamino with the acyl group being alkyl of one to twelvecarbon atoms, inclusive, and trihalomethyl;R₃ and R₄ are each selectedfrom the group consisting of hydrogen, alkyl of one to four carbonatoms, inclusive, cycloalkyl of three to four carbon atoms, inclusive,aryl of six to twelve carbon atoms, inclusive, aralkyl of seven totwelve carbon atoms, inclusive, and aryl of six to twelve carbon atoms,inclusive, substituted with a group selected from halogen, alkoxy of oneto four carbon atoms, inclusive, nitro, aryloxy with aryl of six totwelve carbon atoms, inclusive, alkyl of one to twelve carbon atoms,inclusive, cycloalkyl of three to eight carbon atoms, inclusive, alkenylof two to twelve carbon atoms, inclusive, aryl of six to twelve carbonatoms, inclusive, and aralkyl of seven to twelve carbon atoms,inclusive; R₅ is selected from the group consisting of hydrogen, fluoro,chloro, bromo, iodo, alkyl of one to twelve carbon atoms, inclusive,cycloalkyl of three to eight carbon atoms, inclusive, alkenyl of two totwelve carbon atoms, inclusive, aryl of six to twelve carbon atoms,inclusive, aralkyl of seven to twelve carbon atoms, inclusive, alkoxy ofone to twelve carbon atoms, inclusive, halogen substituted alkyl of oneto twelve carbon atoms, inclusive, halogen substituted cycloalkyl ofthree to eight carbon atoms, inclusive, halogen substituted alkenyl oftwo to twelve carbon atoms, inclusive, halogen substituted aryl of sixto twelve carbon atoms, inclusive, and halogen substituted aralkyl ofseven to twelve carbon atoms, inclusive; R₆ and R₇ are each selectedfrom the group consisting of nitro, amino, acylamino with acyl beingalkyl of one to twelve carbon atoms, inclusive, alkylamino with alkyl ofone to twelve carbon atoms, inclusive, dialkylamino with each alkyl ofone to twelve carbon atoms, inclusive, aryloxy with aryl of six totwelve carbon atoms, inclusive, and a group R₅ as previously defined:and n is an integer of from 1 to 2, inclusive; provided that when one ofR₅, R₆ and R₇ is chlorine, the pyridine ring moiety of said compound isattached to the rest of the molecule through the pyridyl ring carbonatom at the four carbon position; and further provided that when R₁ andR₂ are both selected from the group consisting of hydrogen and alkyl ofone to six carbon atoms, inclusive, said compound is selected from thosewherein R₇ is selected from the group consisting of cycloalkyl of threeto eight carbon atoms, inclusive, aryl of six to twelve carbon atoms,inclusive, aralkyl of seven to twelve carbon atoms, inclusive, alkenylof two to twelve carbon atoms, inclusive, amino, acylamino with acylbeing alkyl from one to twelve carbon atoms, inclusive, alkylamino withalkyl of one to twelve carbon atoms, inclusive, dialkylamino with eachalkyl being one to twelve carbon atoms, inclusive, and aryloxy with arylof six to twelve carbon atoms, inclusive; and those compounds wherein R₄is selected from the group consisting of cycloalkyl of three to sixcarbon atoms, inclusive, aryl of six to twelve carbon atoms, inclusive,aralkyl of seven to twelve carbon atoms, inclusive, and aryl substitutedwith a group selected from the group consisting of halogen, alkoxy ofone to four carbon atoms, inclusive, nitro, aryloxy with aryl of six totwelve carbon atoms, inclusive, alkyl of one to twelve carbon atoms,inclusive, cycloalkyl of three to eight carbon atoms, inclusive, alkenylof two to twelve carbon atoms, inclusive, aryl of six to twelve carbonatoms, inclusive, and aralkyl of seven to twelve carbon atoms,inclusive.
 2. A compound in accordance with claim 1 wherein R₁, R₅ andR₆ are hydrogen; R₂ is selected from the group consisting of hydrogen,halogen, alkyl of one to four carbon atoms, inclusive, alkoxy of one tofour carbon atoms, inclusive, and trifluoromethyl; R₃ and R₄ are thesame or different and are selected from the group consisting ofhydrogen, alkyl of one to four carbon atoms, inclusive, and phenyl; R₇is selected from the group consisting of hydrogen, fluoro, chloro,bromo, iodo, alkyl of one to four carbon atoms, inclusive, alkoxy of oneto four carbon atoms, inclusive, trifluoromethyl, and nitro; n is one totwo, provided that when R₇ is chloro, the pyridine ring moiety isattached to the alkylene at the 4-carbon position; and further providedthat when R₂ is hydrogen or alkyl of one to four carbon atoms,inclusive, then R₇ is trifluoromethyl or nitro and R₄ is phenyl.
 3. Thecompound of claim 1 which is 1,1-diphenyl-3-(3-pyridylmethyl)urea. 4.The compound of claim 1 which is 1,1-diphenyl-3-(4-pyridylmethyl)urea.5. The compound of claim 1 which is 1,1-diphenyl-3-(2-pyridylethyl)urea.6. The compound of claim 1 which is1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea.
 7. The compound of claim 1which is 1,1-diphenyl-3-methyl-3-(2-pyridylethyl)urea hydrochloride. 8.A compound selected from those of the formula: ##STR14## and apharmaceutically acceptable acid addition salt thereof wherein R₁ and R₂are each selected from the group consisting of hydrogen, halogen, alkylof one to six carbon atoms, inclusive, cycloalkyl of three to six carbonatoms, inclusive, alkenyl of two to six carbon atoms, inclusive, phenyl,alkoxy of one to twelve carbon atoms, inclusive, nitro, amino,alkylamino with alkyl of one to twelve carbon atoms, inclusive,dialkylamino with each alkyl of one to twelve carbon atoms, inclusive,acylamino with acyl being alkyl of one to twelve carbon atoms,inclusive, and trihalomethyl;R₃ and R₄ are each selected from the groupconsisting of hydrogen, alkyl of one to four carbon atoms, inclusive,cycloalkyl of three to four carbon atoms, inclusive, aryl of six totwelve carbon atoms, inclusive, aralkyl of seven to twelve carbon atoms,inclusive, and aryl of six to twelve carbon atoms, inclusive,substituted with a group selected from the group consisting of halogen,alkoxy of one to four carbon atoms, inclusive, nitro, aryloxy with arylof six to twelve carbon atoms, inclusive, alkyl of one to twelve carbonatoms, inclusive, cycloalkyl of three to eight carbon atoms, inclusive,alkenyl of two to twelve carbon atoms, inclusive, aryl of six to twelvecarbon atoms, inclusive, and aralkyl of seven to twelve carbon atoms,inclusive; R₅ is selected from the group consisting of hydrogen, fluoro,chloro, bromo, iodo, alkyl of one to twelve carbon atoms, inclusive,cycloalkyl of three to eight carbon atoms, inclusive, alkenyl of two totwelve carbon atoms, inclusive, aryl of six to twelve carbon atoms,inclusive, aralkyl of seven to twelve carbon atoms, inclusive, alkoxy ofone to twelve carbon atoms, inclusive, halogen substituted alkyl of oneto twelve carbon atoms, inclusive, halogen substituted cycloalkyl ofthree to eight carbon atoms, inclusive, halogen substituted alkenyl oftwo to twelve carbon atoms, inclusive, halogen substituted aryl of sixto twelve carbon atoms, inclusive, and halogen-substituted aralkyl ofseven to twelve carbon atoms, inclusive; R₆ and R₇ are each selectedfrom the group consisting of nitro, amino, acylamino with acyl beingalkyl of one to twelve carbon atoms, inclusive, alkylamino with alkyl ofone to twelve carbon atoms, inclusive, dialkylamino with each alkyl ofone to twelve carbon atoms, inclusive, aryloxy with aryl of six totwelve carbon atoms, inclusive, and a group R₅ as previously defined;and n is an integer of from 1 to 2, inclusive; provided that when one ofR₅, R₆ and R₇ is chloro, the pyridine ring moiety of said compound isattached to the rest of the molecule through the pyridyl ring carbonatom at the 4-carbon position.
 9. The compound of claim 8 which is1-(2-nitrophenyl)-3-(2-pyridylethyl)urea-N-oxide.
 10. The compound ofclaim 8 which is 1,1-diphenyl-3-(2-pyridylethyl)urea-N-oxide.
 11. Thecompound of claim 8 which is 1-(4-pyridylmethyl)-3-phenylurea-N-oxide.